Radiotherapy is the application of high-energy ionizing radiation to treat diseases and abnormal tissues in patients. Typically, the radiation is collimated into a beam and directed towards a target area for treatment. A high enough radiation doses will kills the targeted cells. Radiotherapy is typically characterized by a low dose per fraction (e.g., 100-200 centigray), shorter fraction times (e.g., 10 to 30 minutes per treatment) and hyper-fractionation (e.g., 30 to 45 fractions). A ring gantry-based system tends to exhibit relatively high mechanical stability, i.e., less of the deformation problems, and thus can reproducibly and accurately position the radiation source. The ring gantry having radiotherapy apparatus generates stereotactic images and CBCT (Cone Beam Computed Tomography) image. These are the diagnostic tools for providing a type 3-D volumetric image with considerable prospects.
Various types of conventional ring gantries are known in the prior art, wherein most of them typically include dual KV sources and dual flat panel detectors to generate CBCT image and stereotactic image. In the existing U.S. Pat. No. 8,536,547, it is proposed for the creation of CBCT image using a first imaging source and a first imaging detector in the ring gantry. The imaging detectors are fixably mounted in the inner periphery of the ring gantry. In this invention, the produced or captured CBCT image does not provide a greater FOV (Field Of View) with respect to the patient plane.
Typically, the radiotherapy machines which use dual detectors and dual KV image source for stereotactic imaging are not capable of taking a CBCT image with half fan mode and hence they cannot produce a CBCT for higher field of view (greater than 250×250 mm). In order to generate CBCT image with FOV greater than 250×250 mm, there is need of a different machine which has a feasibility to take a CBCT image for larger volumes. In conventional radiotherapy machines with ring gantry, there is no electron mode and customers have to depend on other machines to deliver electron therapy.
Hence, there is need of an apparatus which includes single ring gantry machine to generate both photon beam and electron beam and an imaging system which can generate both CBCT image with greater FOV and stereotactic imaging which is simple and durable.